Theory of operation single phase induction generator at load state , Thesis

Theory of operation single phase induction generator at load state , - Thesis Example , the excitation voltage and frequency vary depending on the rotor speed, the values of the capacitance and the winding inductance and the load current. For any value of capacitance, there is a minimum rotor speed at which self-excitation would occur [1]. It is difficult to measure the self inductance of the generator winding directly. An approximation can be made by driving the rotor at synchronous speed and measuring the stator voltage and current. At the rotor synchronous speed, no current is induced in the rotor and it is a virtual open circuit. The measured impedance (V/I) can be approximated for the winding self-inductance. From the above equations, it is clear that the self-inductance of the winding would vary with the voltage induced in the winding. The variation of magnetizing inductance with voltage for a specific induction generator is shown in Fig 2. b) For a given speed of the rotor, the voltage generated in the winding would vary with the value of the connected parallel capacitor. The relationship between the terminal voltage and the value of the capacitor for a specific induction generator is shown in Fig 3. One requirement in any electrical generator is for the terminal voltage to remain constant when the connected load varies. Most electrical loads operate satisfactorily only in a narrow range around their rated voltage. The value of capacitance needed to maintain constant terminal voltage at a given rotor speed is shown in Fig 4 for a specific induction generator. The graph shows that the variation is linear. In addition to the constant voltage, an alternating current generator also needs to supply power at a constant frequency. For the single phase self-excited generator, we know from induction motor theory that as the load current changes, the slip between the rotor and the stator would vary and cause the induced stator frequency to vary. This relationship for a specific induction generator is shown in Fig 5. 1. Robinson, L. and Holmes,